Very many thanks for your reply. Have made the change and it works.
Just as an aside, the result is a bit disappointing on a Windows platform (though not your fault of course!).
For info, each of my panels has a line of text at the top of about 60 characters. Arial Bold 12pt.
As the panel slides this text blurs horribly, presumably as it tries to redraw itself. Looks awful. On a Mac it is not noticeable, but on Windows... I tried Freeze Window but no good. This happens on 14, 15 and 16.
Anyway, I have added a bit more scripting to hide this line of text as the panel slides, then unhide it once the new panel is showing. Result is fine but a shame about the blurring in the first place.
Many thanks for your help once again.